Conductive Polymer Composition for Uniform OLED Hole Injection Films
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Solution Overview
Problem
Existing conductive polymer compositions used in organic thin-film devices face issues such as moisture retention, film defects, high surface roughness, and non-uniformity, particularly when applied as hole injection layers in organic electroluminescent devices, leading to decreased device performance and longevity.
Innovation Solution
A conductive polymer composition comprising a π-conjugated polymer, a specific dopant polymer, water, a water-soluble organic solvent, and a compound with a fluorinated acid unit, which reduces acidity, improves film formability, and ensures uniformity, even with droplet-application methods like spray coating or inkjet printing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If PSS with high hydrophilicity is used as a dopant to improve dispersibility, then the composite disperses well in water, but a large amount of moisture remains in the film after formation
Solution Approach 1:
The patent modifies the dopant polymer structure by introducing fluorinated groups (e.g., perfluoroalkyl groups) to change the hydrophilicity parameter. This reduces the moisture retention in the film while maintaining adequate dispersibility, resolving the contradiction between good dispersion and excessive moisture content.
Solution Approach 2:
The patent uses composite dopant polymers combining hydrophilic sulfonic acid groups with hydrophobic fluorinated groups. This composite structure achieves a balance between water dispersibility and moisture retention, allowing the material to disperse well in water during processing but retain less moisture in the final film.
2Reliability
If PSS is used as a dopant to achieve high conductivity, then the material shows good electro-conductivity, but the film surface becomes rough and non-uniform
Solution Approach 1:
The patent changes the molecular weight parameter of the dopant polymer and the doping ratio to optimize both conductivity and film uniformity. By controlling these parameters, the patent achieves good electro-conductivity while maintaining smooth and uniform film surfaces suitable for device fabrication.
Solution Approach 2:
The patent introduces fluorinated groups at specific positions in the dopant polymer structure to locally modify properties. This localized modification improves film uniformity and reduces surface roughness while maintaining the overall conductivity through the sulfonic acid groups.
3Ease of manufacture
If the composite is dispersed in water for easy coating, then the material can be applied by spray coating or inkjet printing, but the acidity causes device performance degradation
Solution Approach 1:
The patent designs composite dopant polymers that combine sulfonic acid groups (for conductivity and water solubility) with fluorinated groups (for reduced acidity and improved stability). This composite structure maintains the benefits of water-based coating while mitigating the harmful acidity effect on device performance.
Solution Approach 2:
The patent converts the harmful acidity of sulfonic acid groups into a beneficial property by introducing fluorinated groups that reduce the overall acidity while maintaining water solubility. The fluorinated groups act as a buffer, allowing the material to be processed in water-based solutions without causing device degradation.
4Reliability
If conventional dopant polymers are used to achieve conductivity, then the material shows electro-conductivity, but light absorption in the visible range reduces transparency
Solution Approach 1:
The patent changes the optical properties parameter by introducing fluorinated groups with low polarizability and specific molecular weight optimization. These parameter changes reduce light absorption in the visible range, improving transparency while maintaining the electro-conductivity provided by the sulfonic acid doping.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The composition forms a defect-free, flat, and transparent conductive film with controlled conductivity, reducing residual moisture and preventing unwanted light emission, thereby enhancing the performance and longevity of organic electroluminescent devices.
Implementation Method 1
A polymer having a conjugated double bond (a π-conjugated polymer) does not exhibit electrical conductivity by itself, but becomes an electro-conductive polymer material by doping with an appropriate anion molecule which causes electron or hole to move.
Implementation Method 2
a compound (E) shown by the following general formula (2), wherein an electric conductivity of a film with a thickness of 20 to 200 nm formed from the conductive polymer composition is less than 1.00E-05 S/cm
Data Source
AI summary
An object is to obtain a composition capable of: forming a uniform film even by spray coating or even when the composition is applied in the form of ink for inkjet printing; and preventing light emission from a portion other than an ITO electrode surface when the film is mounted on an organic EL device and light is emitted from the device. A conductive polymer composition contains: a composite containing a π-conjugated polymer (A) and a polymer (B) shown by a general formula (1); H2O (D) for dispersing the composite; a water-soluble organic solvent (C); and a compound (E) shown by a general formula (2). The electric conductivity of a film with a thickness of 20 to 200 nm formed from the conductive polymer composition is less than 1.00E-05 S/cm.